Various methods and machines have been used in the past to measure electrical characteristics of living tissue for the purpose of locating an area of abnormal nervous system activity. U.S. Pat. No. 4,697,599, issued Oct. 6, 1987, to William Woodley and David Longmire describes such an apparatus and its use. This patent should be carefully considered for the purpose of putting the present invention into proper context.
A device known as the EPI-SCAN 5000, manufactured by the Epi-Scan Corporation of Russellville, Ala., represents an embodiment of the U.S. Pat. No. 4,697,599. One clinical use of this device is to objectively assess mediation, maintenance or clinical expression of certain pain forms through the sympathetic nervous system. Localized variance in skin conductance levels can be an indication of sympathetically-mediated or maintained pain. Detection of such abnormalities may be used to indicate certain pain therapies, such as insertion of a "nerve block."